Both TGF-β1 and Smad4 regulate type I collagen expression in the muscle of grass carp,Ctenopharyngodon idella

Fish Physiology and Biochemistry - Type I collagen is proven to make an important contribution to fish muscle quality. Our previous study has shown the Smad4-dependent regulation of type I collagen...     

新柴牌中大功率农机动力的开发

在N,D,K等3个系列产品平台上整合开发了18.4～58.8kW中大功率农机动力,目的是有一个相对较宽的产品链来配套中大功率拖拉机及相应功率要求的联合收割机。其产品开发的重点:一是功率谱完整,即通过缸径冲程的组合设计,力求在同一条生产线上制造不同功率的产品;二是同系列同缸心距扩排量带来的结构可靠性开发,主要是缸套-活塞环的可靠性开发及曲轴与轴承的可靠性开发,满足农用动力特殊工况和工作环境的可靠性开发;三是满足国内非道路移动机械二阶段排放要求的性能开发,特别是PM,NOx和燃油消耗之间的折中,重点是在经济成本的条件下对燃烧系统和燃油系统的优化开发。     

叶片出口角对离心泵性能曲线形状的影响

采用FLUENT,在多重参考坐标系下,利用有限体积法对雷诺时均Navier-Stokes方程进行数值离散,选用标准k-ε湍流模型和SIMPLEC方法求解,对4台不同比转速离心泵在不同叶片出口角下的内部流场进行了叶轮和蜗壳的多工况耦合数值模拟,研究了叶片出口角对离心泵扬程曲线和效率曲线的影响并进行了实验验证.研究给出了性能曲线随叶片出口角变化的规律并指出叶片出口角的改变对高比转速泵的扬程和效率曲线形状影响最为明显.研究结果对离心泵的选型和性能改进具有一定的指导意义.     

国内外农业信息化建设对佳木斯地区的启示

分析借鉴国内外农业信息化建设的经验,对加快实现佳木斯地区农业的信息化具有重要意义.为此,当前世界上农业信息化建设工作比较发达的欧美国家信息化建设的工作经验;分析了开展此项工作相对较晚的亚洲国家农业信息化建设的情况以及我国近年来农业信息化工作的情况.由此得出国内外经验给佳木斯地区开展农业信息化建设工作的4点启示:一是发挥政府的宏观调控职能是开展好农业信息化建设的保障;二是健全基础设施是开展好农业信息化建设的前提;三是搞好信息数据库建设是开展好农业信息化建设的基础;四是做好科研、教育和推广的有机结合是开展好农业信息化建设的必然.     

Presettlement and modern disturbance regimes in coast redwood forests: Implications for the conservation of old-growth stands

Coast redwood (Sequoia sempervirens), a western North American conifer of ancient lineage, has a paradoxical combination of late-successional characteristics and strong adaptations to disturbance. Despite its shade tolerance and heavy dominance of the canopy on many sites, redwood saplings are uncommon in upland old-growth stands. Information needed to ensure the conservation of old-growth redwood forests has been limited. In this review paper, we integrate evidence on redwood biology with data on the historic and modern disturbance regimes to help clarify the degree to which key attributes of redwood forests may have been dependent upon periodic disturbance. Available evidence suggests that episodes of fire, flooding, and slope failure prior to European settlement were frequent but predominantly of low to moderate severity and extent, resulting in broadly uneven-aged forests. The majority of fires prior to European settlement were apparently of human origin. Frequency and severity of the major disturbance agents have been radically changed in modern times. Fires have been largely excluded, and flooding has been altered in ways that have often been detrimental to old-growth redwoods on alluvial terraces. However, because of the apparent anthropogenic origin of most presettlement fires, the long-term evolutionary role of fire for coast redwood is ecologically ambiguous. With fire exclusion, redwood possibly could be displaced to some extent on upland sites by increasing abundance of fire-sensitive competitors. Alternatively, redwood may be able to maintain dominance by vegetative sprouting and new seedling establishment on root-wad mounds, fallen logs, and on soil exposed by slope failure. Future research priorities are suggested that will help resolve some of the current ambiguities.     

现有生物质能转换利用技术综合评价

本文介绍了生物质能转换利用的方法,对现有生物质能转换技术进行了比较,运用层次分析法从技术先进性、经济可行性和环境安全性三个方面对现有生物质能转换利用技术进行了综合评价,提出了生物质能转换利用技术的优先发展顺序和发展方向,为我国生物质能转换利用技术的发展和应用提供参考依据.     

森林生态系统土壤碳库对氮沉降的响应研究进展

大气氮沉降的不断加剧,改变了土壤理化性质,直接影响植物的生长与发育,间接影响了陆地生态系统碳库,进而可能改变全球气候变化进程。森林是陆地生态系统的主体,因此,弄清氮沉降如何影响森林生态系统碳库,对预测全球气候变化具有重要意义。笔者旨在详细分析氮沉降对森林生态系统土壤碳库输入和输出的影响,阐述氮沉降对森林生态系统凋落物分解、细根周转和土壤呼吸的影响研究进展和作用机制。截至目前,关于氮沉降对于陆地生态系统的影响研究报道较多,且国内外诸多学者也在森林生态系统土壤碳库对氮沉降的响应领域开展了较多试验研究,但多集中于碳输入和输出的总量分析,而对输入和输出各个组分的研究相对较少。笔者综述了国内外有关森林生态系统碳库输入和输出各组分对氮沉降响应的相关研究,为进一步揭示其响应机制和途径提供参考依据。     

Genetic interpretations of the effects of bulk breeding on four populations of beans (Phaseolus vulgaris L.)

Summary The effects of bulk breeding on yield and its components in two high-yeilding and two low-yielding bean populations when grown at crop densities are interpreted in terms of gene action and selection. There was considerable additive variation in the crosses, dominance effects were variable but tended to be negative. The results were compared with results obtained at low density by another worker with the same populations, and this showed that interpretations of gene action in hybrid vigour depend on the test environment used. The interpretations were also compared with plant breeding interpretations made on the same material (Hamblin, 1977), and it was found that a single pattern of response to natural selection, in plant breeding terms, may be explained by more than one genetic interpretation and, conversely, a single genetic interpretation may result in different patterns of response in plant breeding terms. The value of composite crosses in plant breeding are discussed and it is concluded that there is a greater chance of producing improved lines from a large number of simple crosses than from a smaller number of composite crosses.     

REDD+机制各缔约方观点总结分析及我国对策建议

减少发展中国家毁林及森林退化引起的温室气体排放, 森林保护、可持续森林管理和增加森林碳储量(REDD+)在减缓气候变化行动中的作用越来越明显, 已经成为《联合国气候变化框架公约》谈判的重要议题。近年来各缔约方针对方法学、融资机制和REDD+与清洁发展机制(CDM)关系的谈判争论越来越激烈。在《联合国气候变化框架公约》第18次缔约方会议(COP18)期间, 对REDD+议题提出了新的要求, 除了有关于逐步建立国家水平森林参考排放水平或参考水平等有关方法学的技术与科学问题外, 基金在融资机制中的作用和非碳效益支付议题也有待进行深入的磋商。文中基于对各缔约方提案的分析结果和REDD+示范项目开展情况, 结合我国森林资源现状, 分析了REDD+机制对我国可能产生的影响并提出后续谈判期的对策建议。     

孕穗期低温条件下ABA对水稻结实率及叶片生理特性的影响

为了明确ABA对孕穗期低温下水稻结实率及叶片生理特性的调控效应,本试验在盆栽条件下,以2个水稻(Oryza sativa L.)品种‘龙粳11’（冷敏型）和‘龙稻5’（耐冷型）为材料,于孕穗期在人工气候室进行低温（15℃,持续1,2,3,4,5天）处理,并喷施不同浓度的脱落酸(ABA),研究低温条件下ABA对不同水稻结实率的调控效应,同时探讨了ABA和低温对水稻叶片膜透性、抗氧化酶等生理特性的影响。结果表明：低温条件下,‘龙稻5’的结实率变化不大,‘龙粳11’的结实率显著降低,20 mg/L的ABA能够有效缓解低温伤害,相对提高低温胁迫下水稻的结实率。叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性表现出先升高后下降的变化趋势,‘龙稻5’的抗氧化酶活性、可溶性糖和可溶性蛋白含量高于‘龙粳11’,但丙二醛(MDA)含量和相对电导率低于‘龙粳11’。ABA可提高冷敏品种的抗氧化酶活性、可溶性糖和可溶性蛋白的含量,同时可降低MDA含量和相对电导率。这说明ABA可以通过调控水稻抗氧化酶、可溶性糖等生理指标的活性及含量,进而提高冷敏水稻品种的耐冷性。